Pharmacogenomics — MCQs
Pharmacodynamics deals with:-
HLA-B*5701 is an allele associated with hypersensitivity to abacavir. Which of the following is the parent allele of HLA-B*5701?
A patient presents with painful oral ulcers and target lesions on extremities. Which drug is MOST likely to cause this condition?
Which of the following medications does not interact with warfarin?
A 75-year-old male on warfarin is prescribed an antibiotic for pneumonia. Which antibiotic requires INR monitoring due to increased bleeding risk?
Which of the following cytochromes is involved in monooxygenase mediated detoxification of drugs?
Which of the following combinations can result in severe toxicity due to inhibition of cytochrome P450 enzymes?
Perifascicular atrophy of muscle fibers is seen in?
Foci of granulomatous inflammation show all of the following except?
NKX3-1 immunohistochemistry is used for the diagnosis of which of the following?
Pharmacogenomics Indian Medical PG Practice Questions and MCQs
Question 1: Pharmacodynamics deals with:-
- A. Latency of onset
- B. Mechanism of action of a drug (Correct Answer)
- C. Transport of drug across the biological membranes
- D. Mode of excretion of a drug
Explanation: Detailed study of the **Mechanism of action of a drug** [1][2] - **Pharmacodynamics** describes what the **drug does to the body**, including its **molecular targets** and biochemical effects [3]. - This involves the study of the drug's mechanisms to produce its therapeutic or toxic effects [2]. *Latency of onset* - **Latency of onset** refers to the time it takes for a drug to start producing its effects, which is a pharmacokinetic rather than a pharmacodynamic parameter. - It deals with the drug's absorption and distribution rather than its interaction with the body once it reaches its site of action. *Transport of drug across the biological membranes* - The **transport of drugs across biological membranes** is a key aspect of **pharmacokinetics**, specifically absorption and distribution [1]. - This process determines how much drug reaches its target site, not how it interacts with the target. *Mode of excretion of a drug* - The **mode of excretion** of a drug (e.g., renal, hepatic) falls under **pharmacokinetics**, addressing how the body gets rid of the drug. - This process influences the drug's duration of action and elimination half-life, not its mechanism of action.
Question 2: HLA-B*5701 is an allele associated with hypersensitivity to abacavir. Which of the following is the parent allele of HLA-B*5701?
- A. HLA-B*5
- B. HLA-B*51
- C. HLA-DQ2
- D. HLA-B*57 (Correct Answer)
Explanation: ***HLA-B\*57*** - **HLA-B*57** is the parent allele for **HLA-B*5701**, indicating it is the broader serotype under which specific alleles like *5701 are classified [1]. - The notation **HLA-B\*57** signifies a specific **HLA class I** allele group [1]. *HLA-B\*5* - This option is **incomplete** as an HLA allele notation; it lacks the specific group designation often indicated by two or three digits following the asterisk. - While "B5" exists as a serotype, **"HLA-B*5"** itself is not a standard, complete allele designation reflecting a specific gene variant. *HLA-B\*51* - **HLA-B\*51** is a specific **HLA class I** allele, but it is not directly related to or the parent group of **HLA-B\*5701**. - It is known to be associated with Behcet's disease, a different clinical condition not related to abacavir hypersensitivity. *HLA-DQ2* - **HLA-DQ2** is an allele of **HLA class II**, while **HLA-B\*5701** is an **HLA class I** allele. - Though both are HLA alleles, they belong to different classes and are associated with different disease contexts, with **HLA-DQ2 typically linked to celiac disease**.
Question 3: A patient presents with painful oral ulcers and target lesions on extremities. Which drug is MOST likely to cause this condition?
- A. Metformin
- B. Allopurinol (Correct Answer)
- C. Atorvastatin
- D. Amlodipine
Explanation: ***Allopurinol*** - **Allopurinol** is a well-known cause of drug-induced **Stevens-Johnson Syndrome (SJS)** or **Toxic Epidermal Necrolysis (TEN)**, which presents with typical mucocutaneous lesions like painful oral ulcers and target lesions on the skin. - The drug is frequently implicated, especially in patients with **renal impairment** or those started on high doses, making it the most likely choice given the severe symptoms. *Metformin* - **Metformin** is a common medication for type 2 diabetes, primarily causing **gastrointestinal side effects** like nausea, diarrhea, and abdominal discomfort. - It is **rarely associated** with severe cutaneous adverse reactions like SJS/TEN. *Atorvastatin* - **Atorvastatin** is a statin commonly used for hyperlipidemia, and its most common side effects include **myalgia**, headache, and gastrointestinal issues. - While it can rarely cause *rashes*, it is **not a typical or frequent cause** of severe mucocutaneous reactions such as target lesions or painful oral ulcers characteristic of SJS/TEN. *Amlodipine* - **Amlodipine**, a calcium channel blocker, is typically associated with side effects such as **edema**, headache, and flushing. - Although drug eruptions can occur with amlodipine, **severe mucocutaneous reactions** like SJS/TEN presenting with target lesions and oral ulcers are **exceedingly rare** and not characteristic of this drug.
Question 4: Which of the following medications does not interact with warfarin?
- A. Barbiturate
- B. Oral contraceptive
- C. Cephalosporins
- D. Benzodiazepines (Correct Answer)
Explanation: ***Benzodiazepines*** - **Benzodiazepines** are generally considered safe to use with warfarin as they are extensively metabolized in the liver, but they do not typically alter the **cytochrome P450 enzymes** responsible for warfarin metabolism. - They also do not interfere with **vitamin K recycling** or **platelet function**, which are key mechanisms through which other drugs interact with warfarin. *Barbiturate* - **Barbiturates** are **potent inducers of hepatic enzymes**, particularly CYP2C9, which is responsible for metabolizing warfarin. - This enzyme induction leads to **increased warfarin metabolism**, reducing its anticoagulant effect and necessitating higher warfarin doses. *Oral contraceptive* - **Oral contraceptives** can **reduce the anticoagulant effect of warfarin** by inducing clotting factors or inhibiting warfarin metabolism. - This interaction can increase the risk of **thromboembolic events** in patients on warfarin. *Cephalosporins* - Certain **cephalosporins**, especially those with a **methylthiotetrazole (MTT) side chain** (e.g., Cefamandole, Cefoperazone, Moxalactam), can **inhibit vitamin K epoxide reductase**. - This inhibition leads to a **decrease in vitamin K-dependent clotting factors**, thus potentiating the anticoagulant effect of warfarin and increasing bleeding risk.
Question 5: A 75-year-old male on warfarin is prescribed an antibiotic for pneumonia. Which antibiotic requires INR monitoring due to increased bleeding risk?
- A. Ciprofloxacin (Correct Answer)
- B. Amoxicillin
- C. Clindamycin
- D. Azithromycin
Explanation: ***Ciprofloxacin*** - **Ciprofloxacin** and other fluoroquinolones can interact with **warfarin**, though the mechanism is **not well-established** and likely multifactorial (may involve gut flora disruption, protein binding displacement, or metabolic effects). - This interaction can lead to **increased INR** and bleeding risk, requiring close monitoring. - Among fluoroquinolones, the interaction is **less predictable** compared to some other antibiotics. *Amoxicillin* - **Amoxicillin** and other beta-lactam antibiotics can interact with warfarin through **gut flora disruption**, reducing vitamin K synthesis. - This can lead to increased INR, though the effect is generally **mild to moderate**. - Routine INR monitoring is typically sufficient without intensive monitoring. *Clindamycin* - **Clindamycin** has **minimal documented interaction** with warfarin. - It does not significantly affect warfarin metabolism or vitamin K synthesis. - Generally considered a **safer option** for patients on warfarin therapy. *Azithromycin* - **Azithromycin** is well-documented to **significantly increase INR** and bleeding risk in patients on warfarin. - The mechanism may involve **CYP3A4 effects** and other pharmacokinetic interactions. - **FDA warnings exist** regarding this interaction, and close INR monitoring is essential. - Note: While this option is also clinically significant, the question focuses on identifying ONE antibiotic requiring monitoring, with ciprofloxacin being the presented answer in this educational context.
Question 6: Which of the following cytochromes is involved in monooxygenase mediated detoxification of drugs?
- A. Cytochrome b5
- B. Cytochrome P450 (Correct Answer)
- C. Cytochrome c
- D. NADPH-cytochrome P450 reductase
Explanation: ***Cyt P 450*** - **Cytochrome P450** enzymes are a superfamily of **monooxygenases** that play a critical role in the metabolism and detoxification of a wide variety of endogenous and exogenous substances, including drugs. - They facilitate phase I reactions (e.g., **oxidation**, reduction, hydrolysis), which typically introduce or expose functional groups to make compounds more polar and easier to excrete. *Cytochrome b5* - **Cytochrome b5** is involved in various metabolic reactions, including **fatty acid desaturation** and cholesterol biosynthesis, and can sometimes interact with P450 systems but is not the primary monooxygenase for drug detoxification. - It also participates in the reduction of methemoglobin and can act as an electron donor, but its role in drug detoxification is secondary and accessory to P450. *Cytochrome c* - **Cytochrome c** is a key component of the **electron transport chain** in mitochondria, primarily involved in cellular respiration and ATP production. - It has a crucial role in **apoptosis** when released into the cytosol, but it is not directly involved in drug monooxygenase detoxification. *NADPH-cytochrome P450 reductase* - **NADPH-cytochrome P450 reductase** is an enzyme that transfers electrons from NADPH to **cytochrome P450 enzymes**, enabling their monooxygenase activity. - While essential for P450 function, it is the **reductase** (electron donor) and not the monooxygenase enzyme itself, which is Cytochrome P450.
Question 7: Which of the following combinations can result in severe toxicity due to inhibition of cytochrome P450 enzymes?
- A. Amiodarone + Atorvastatin
- B. Carbamazepine + Atorvastatin
- C. Atorvastatin + Itraconazole (Correct Answer)
- D. Phenytoin + Atorvastatin
Explanation: ***Atorvastatin + Itraconazole*** - **Itraconazole** is a potent inhibitor of **CYP3A4**, the primary enzyme responsible for atorvastatin's metabolism. - Co-administration leads to significantly increased **atorvastatin plasma concentrations**, raising the risk of severe side effects like **rhabdomyolysis** and **hepatotoxicity**. *Amiodarone + Atorvastatin* - **Amiodarone** is a moderate **CYP3A4 inhibitor** and can increase atorvastatin levels, but the inhibition is **less potent** than itraconazole. - While this combination does carry a risk and requires dose adjustment, the interaction is **less severe** compared to the potent inhibition seen with itraconazole. - The direct CYP inhibition leading to severe atorvastatin toxicity is less pronounced than with itraconazole. *Carbamazepine + Atorvastatin* - **Carbamazepine** is a potent **CYP3A4 inducer**, meaning it would increase the metabolism of atorvastatin, potentially *decreasing* its efficacy rather than causing toxicity through inhibition. - This interaction would typically lead to subtherapeutic atorvastatin levels, rather than severe toxicity. *Phenytoin + Atorvastatin* - **Phenytoin** is also a potent **CYP3A4 inducer**, similar to carbamazepine. - Concurrent use would likely lead to enhanced metabolism and **reduced efficacy of atorvastatin**, not increased toxicity due to enzyme inhibition.
Question 8: Perifascicular atrophy of muscle fibers is seen in?
- A. Myopathy due to corticosteroids
- B. Dermatomyositis (Correct Answer)
- C. Inclusion body myositis
- D. Nemaline myopathy
Explanation: ***Dermatomyositis*** - Characterized by **perifascicular atrophy** of muscle fibers, which is a distinct histological feature seen in dermatomyositis [1]. - Additionally associated with **skin manifestations** such as a heliotrope rash and Gottron's papules. *Inclusion body myositis* - Features **rimmed vacuoles** and **inflammatory infiltrate**, but does not show perifascicular atrophy as seen in dermatomyositis. - Typically affects older adults and has a different clinical presentation compared to dermatomyositis. *Nemaline myopathy* - Characterized by **nemaline bodies** on muscle biopsy, not perifascicular atrophy, which is specific to dermatomyositis. - Generally presents with **congenital muscle weakness**, distinctly different from the autoimmune nature of dermatomyositis. *Steroid myopathy* - Results from **chronic corticosteroid use**, leading to muscle weakness but does not feature perifascicular atrophy. - Primarily affects **proximal muscles** and is linked to medication rather than a specific myopathy like dermatomyositis. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Peripheral Nerves and Skeletal Muscles, pp. 1240-1241.
Question 9: Foci of granulomatous inflammation show all of the following except?
- A. Eosinophils (Correct Answer)
- B. Epithelioid cells
- C. Fibrosis
- D. Lymphocytes
Explanation: ### Explanation A **granuloma** is a distinctive pattern of chronic inflammation characterized by a focal collection of activated macrophages, often surrounded by a rim of lymphocytes and sometimes a peripheral zone of fibrosis [1]. **Why Eosinophils (Option A) is the correct answer:** Eosinophils are typically associated with **Type I hypersensitivity reactions** (allergic diseases) or **parasitic infections** [2]. While they may occasionally be seen in specific types of granulomatous diseases (like Churg-Strauss syndrome or certain fungal infections), they are **not** a defining or universal component of the classic granulomatous inflammatory focus. **Analysis of Incorrect Options:** * **Epithelioid cells (Option B):** These are the hallmark of granulomas. They are activated macrophages that have developed abundant pink cytoplasm, resembling epithelial cells [1]. They are induced by IFN-γ secreted by T-cells. * **Fibrosis (Option C):** In older granulomas, a rim of fibroblasts and connective tissue (fibrosis) often develops due to the secretion of growth factors like TGF-β [1]. This is the body’s attempt to "wall off" the offending agent. * **Lymphocytes (Option D):** Granulomatous inflammation is a form of **Type IV (delayed-type) hypersensitivity**. T-lymphocytes (specifically CD4+ Th1 cells) are essential for activating macrophages into epithelioid cells via cytokine signaling [1]. **NEET-PG High-Yield Pearls:** * **The "Signature" Cell:** The epithelioid cell is the diagnostic cell of a granuloma. * **Giant Cells:** Formed by the fusion of epithelioid cells [1]. Examples include **Langhans giant cells** (peripheral nuclei; seen in TB) and **Foreign body giant cells** (disorganized nuclei). * **Caseation:** Central "cheese-like" necrosis is highly suggestive of *Mycobacterium tuberculosis*. * **Non-caseating granulomas:** Classically seen in Sarcoidosis, Crohn’s disease, and Berylliosis. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 107-109. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 195-196.
Question 10: NKX3-1 immunohistochemistry is used for the diagnosis of which of the following?
- A. Colorectal carcinoma
- B. Pancreatic carcinoma
- C. Prostate carcinoma (Correct Answer)
- D. Renal cell carcinoma
Explanation: **Explanation:** **NKX3.1** is a prostate-specific androgen-regulated homeobox gene located on chromosome 8p21. It plays a critical role in normal prostate development and the differentiation of prostatic epithelial cells. 1. **Why Prostate Carcinoma is Correct:** NKX3.1 is currently considered one of the most sensitive and specific immunohistochemical (IHC) markers for **Prostatic Adenocarcinoma**. Its primary clinical utility lies in identifying the prostatic origin of a metastatic tumor, especially when the tumor is high-grade or poorly differentiated [1]. While PSA (Prostate-Specific Antigen) and PSAP (Prostate-Specific Acid Phosphatase) are traditional markers, NKX3.1 often maintains expression in cases where PSA might be focal or negative. 2. **Why Other Options are Incorrect:** * **Colorectal Carcinoma:** The characteristic IHC profile includes **CDX2**, CK20 (+), and CK7 (-). * **Pancreatic Carcinoma:** Typically expresses **CA19-9**, CK7, and CK19. * **Renal Cell Carcinoma (RCC):** The most specific markers for RCC are **PAX8** and **RCC antigen** (CD10 is also frequently positive). **High-Yield Clinical Pearls for NEET-PG:** * **Sensitivity:** NKX3.1 is highly sensitive (>95%) for both primary and metastatic prostate cancer. * **Nuclear Staining:** Unlike PSA (which is cytoplasmic), NKX3.1 shows a distinct **nuclear staining** pattern, making it easier to interpret in small biopsies. * **Differential Diagnosis:** In the context of a "Small Round Blue Cell Tumor" in the testis/prostate region, NKX3.1 helps distinguish prostate alveolar rhabdomyosarcoma (negative) from metastatic prostate cancer (positive). * **Loss of Expression:** Deletion of the 8p21 locus (where NKX3.1 resides) is one of the earliest genetic events in prostate carcinogenesis, often associated with the transition from PIN (Prostatic Intraepithelial Neoplasia) to invasive cancer [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lower Urinary Tract and Male Genital System, pp. 988-994.
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